There should be a 9 digit number stamped in the neck. The 17 digit number is on the white sticker.
I have three XS's registered in NY. The 75 uses the 9 digit #, the 81 uses the 9 digit #. the 83 uses the 17 digit #. They all have the white stickers.
The numbers stamped in the neck can be all digits or have some letters. The 75 is 477108xxx,, the 81 is 4M4007xxx. the 83 is 5V4103xxx.
As far as the registration goes I guess they started using the 17 digits in 82 or 83.
I'll use my 83 number as an example. JYA5V4003DA103xxx. The JYA indicates country of origin and manufacturer, the 5V4 and the last 6 are the frame number. The 003DA I don't know what the mean.
Thomasaun, can you post a pic of the neck showing the sticker and stamped number?
Leo